The present invention relates to an air-fuel control in which the actual air-fuel ratio is detected and is controlled by feedback to the level of the mixture gas supplied to the engine.
In conventional methods so far suggested, in addition to the integration processing control by the output of an air-fuel ratio sensor, a value corresponding to the integration data is stored as correction data or learning value for each condition of the engine so that the air-fuel ratio is controlled by feedback by means of the learning data corresponding to the prevailing engine condition among the correction data thus learned and the integration data associated therewith.
According to the conventional methods, however, the learning is effected always even during unstable state of the engine, and therefore even undesirable data are stored with the result that the air-fuel ratio fluctuates or the engine operability is adversely affected.